| | This package propose a set of abstract persistent
classes. These classes may be sort in three main
groups, which are :
- fuzzy classes
- methods
- dynamic classes
And in two complementary groups used by the
previously described family, which are :
- parameter classes
- variable classes
All the main classes are manipulated through two
steps which are :
- the definition which gives the signature of the
object
- the instanciation which always references a
definition
This separation has been created to clearly
separate the definition of an object, a method or
a class which is the description and the instance
which is the utilisation with a particular set of
values. In this case for few instanciations of
the same object, the definition can be unique.
Each family address a particular problem.
Dynamic class
-------------
This family of classes offers the possibility to
define and to manipulate dynamically objets with
the same specifications as C++ objects.
Dynamically means without CDL description and
without compilation and link if all the methods
attached are interpreted methods.
The first thing to do is to define the signature
of the class, in terms of fields and methods.
You can also derive a class from others, add
fields, and add or redefine methods.
Then instances of the class can be created and
values can be assigned to the fields.
It is then possible to execute methods attached to
the definition of the class. These methods may set
computed values to other fields, or simply return
them.
A method can be compiled or interpreted.
Fuzzy class
-----------
A fuzzy class is a degeneration of a dynamic
class. Only the fields are specified. These
classes are useful to describe objects with
various definitions, and with the number and the
nature of fields depending of the definition.
The definitions of the lights for Photo Realistic
Renderer is an illutration of the use of the fuzzy
classes.
These lights have the same definitions in terms of
parameters as the lights used in the LightWorks
module.
For each type of light an exhaustive set of
parameters is described, and each parameter is
defined by its name, its type and, if necessary,
its default value as follows :
ambient
"intensity" Standard_Real 1.0
"colour" Materials_PColor 1.0 1.0 1.0
distant
"intensity" Standard_Real 1.0
"colour" Materials_PColor 1.0 1.0 1.0
"location" PGeom_CartesianPoint 0.0 0.0 1.0
"to" PGeom_CartesianPoint 0.0 0.0 0.0
"shadows" Standard_Boolean Standard_False
"shadow resolution" Standard_Integer 256
"shadow quality" Standard_Integer 4
"shadow softness" Standard_Real 1.0
eye
"intensity" Standard_Real 1.0
"colour" Materials_PColor 1.0 1.0 1.0
point
"intensity" Standard_Real 1.0
"colour" Materials_PColor 1.0 1.0 1.0
"location" PGeom_CartesianPoint 0.0 0.0 0.0
"fall off" LightWorks_LiFallOffType LI_FALL_OFF_CONSTANT
"shadows" Standard_Boolean Standard_False
"shadow resolution" Standard_Integer 256
"shadow quality" Standard_Integer 4
"shadow softness" Standard_Real 1.0
spot
"intensity" Standard_Real 1.0
"colour" Materials_PColor 1.0 1.0 1.0
"location" PGeom_CartesianPoint 0.0 0.0 1.0
"to" PGeom_CartesianPoint 0.0 0.0 0.0
"fall off" LightWorks_LiFallOffType LI_FALL_OFF_CONSTANT
"cone angle" Standard_Real 60.0
"cone delta angle" Standard_Real 5.0
"beam distribution" Standard_Real 2.0
"shadows" Standard_Boolean Standard_False
"shadow resolution" Standard_Integer 256
"shadow quality" Standard_Integer 4
"shadow softness" Standard_Real 1.0
All these definitions are described in a file
which is read at the first creation of a light
instance to be put in a dictionary.
At the creation of an instance, just a reference
on the definition is set. All the parameter values
are read in the definition. If now a value of one
parameter is changed, the modified parameter is
added to the instance. So only the modified
parameters are directely attached to the instance.
This behaviour allows the use of an instance as
definition, and can be useful to create catalogs
of standards which can be directly questioned in
the database.
The use of fuzzy classes needs four prerequisites
which are :
- The creation of a file with the exhaustive
description of all the possible types taken by an
object and for each type the complete set of
parameters in terms of name, type, and, if
necessary, default value.
- The inheritance from the class
FuzzyDefinitionsDictionary and, if necessary, the
redefinition of the Switch method for the non-
standard type of parameters described in the file.
- The following method :
void DictionaryOfDefinitions(Handle(MyPackage_MyDictionary)&);
must be writen in the file MyPackage.cxx, because
this method is automatically called by the
constructor of FuzzyInstance. This method tests if
the dictionary has been created yet. If it is
true the method returns a reference to it,
otherwise the method creates the dictionary before
returning the reference.
- The instanciation of the FuzzyInstance class
with the pre-defined dictionary.
Method class
------------
The behaviour of these classes are similar to
fuzzy classes. Only the semantic is different.
These classes are for memorized actions or
constraints, e.g. they are useful to memorized
persistently the working system of Imagine
Conception.
More...
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1.6.3